Disk drives typically include one or more sliders configured with read and write heads. An actuator/suspension arm holds a slider above a magnetic disk. When the magnetic disk rotates, air flow generated by the rotation of the magnetic disk causes an air bearing surface (ABS) of the slider to fly at a particular height above the magnetic disk. As the slider flies on the ABS, a voice coil motor (VCM) moves the actuator/suspension arm to position the read and write heads over selected tracks of the magnetic disk.
As the technology has advanced, data densities have increased and track widths and separations have narrowed considerably. In fact, track widths and separations have narrowed so much that writing to one track can affect or “overlap” the data stored on adjacent tracks, a phenomena generally referred to as Adjacent Track Interference (ATI) or Side Track Erasure (STE). As such, Directed Offline Scans (DOS) are periodically performed to identify data degradation on the tracks resulting from these overlap conditions. If the data of a particular track is degrading, the track is re-written. Although useful, DOSs can be quite intensive due to the time to verify the track. And, this can impact the overall performance of the disk drive.